Question

The standard enthalpy of formation of 3 nh is 46kj mol1. If the enthalpy of formation of 2 h from its atoms is 435 kj mol1 and that of nitrogen is 712 kj mol1 , the approximate average bond enthalpy of nh bond in nh3 is:

Answer 1

Given :
2(g) 2(g)
1 N + 3 H
2 2
°
3(g) g NH ;ΔH = –46
1 × 712
2
3 × 436
2
N + 3H (g) (g)
Average bond enthalpy of N–H bond = + 352
kJ mol.